There are Bad People out there, who sell USB flash drives designed to show fake capacity values.
Over the past year, I’ve purchased a few dozen USB flash drives, with capacities ranging from 8GB to 256GB. Some were genuine; most were fakes.
How so? These products are designed using components that provide much less capacity, but with circuits and/or code designed to “fake it” with a higher capacity.
Sometimes, the dubious nature of the products is obvious: if a 64GB device shows “62.4GB available space,” it’s always a fake (because a true 64GB device would actually show 59.3 or 59.4GB available storage capacity). One 256GB Micro SD card actually showed “258GB available space.”
I tested each device (often twice).
The first test is a simple program called h2testw (which you can find here (German) or here (English). It simply writes a series of 1GB files to the device, and then tries to read them back. For devices claiming 64GB storage, the most frequent result was a real capacity of about 14.2GB.
The second test is exactly what you’d expect: copy your own files to fill at least half the drive’s capacity, then check to see if the files are actually there. I copied all my MP3 music, and it seemed to copy just fine, until I tried to play it back. Then, only a small portion of my music was actually accessible.
I’ve managed to get refunds for about a third of these.
My advice: don’t buy from “new” sellers with feedback under 100; read the feedback to see if the seller has been selling storage items for more than a month, and if so, read any complaints (note that many buyers won’t realize the item is fake, until they try to read back the data — which might be months or years later). And note that some self-defined “US Sellers” aren’t in the US at all, but ship from Asia.